Forming system for insulation film

ABSTRACT

The silicon oxide film ( 106 ) and silicon nitride film ( 107 ) are formed by microwave plasma processing with a radial line slot antenna.

TECHNICAL FIELD

The present invention relates to a highly reliable forming method andforming system for insulation film.

BACKGROUND ART

With the high-integration and high-miniaturization of semiconductorintegrated circuits, the miniaturization of Metal InsulatorSemiconductor Field Effect Transistors (MISFET) on the semiconductorintegrated circuits is advancing. With the miniaturization, thethickness of a gate insulator is demanded to be extremely thin, beingabout a couple nanometers.

Generally, silicon oxide (SiO₂) film, which is formed by thermaloxidation of a silicon substrate, is applied as a gate insulator.However, thinning a silicon oxide film to a couple nanometers, hasproblems such as an increase of the gate leakage current (tunnelcurrent), and penetration of impurities from the gate electrode of theMISFET.

To control the increase and so forth of the tunnel current, a stackinggate insulator which has a structure of stacking a higher permittivityfilm (high-permittivity film) onto a thin-silicon oxide film (or asilicon nitride film, or a silicon oxide-nitride film), is beingdeveloped. By applying the stacking gate insulator, physical thicknessis secured to a certain extent, and Equivalent Oxide Thickness (EOT) iskept low. Here, the EOT is a converted value of the thickness of thefilm of the relative permittivity ε and effective film thickness t, tothe thickness of the relative permittivity of the silicon oxide film(εsio₂/ε), and is defined as, EOT=(εsio₂/ε)·t.

A forming method of a stacking gate insulator applying a silicon nitridefilm (SiN film) as a high-permittivity film has been disclosed in theUnexamined Japanese Patent Application KOKAI Publication No.2000-294550. The insulated gate formed by the method disclosed in theaforementioned publication, comprises a direct silicon oxide-nitridefilm (or an oxide film or a nitride film) formed in a thickness of onenanometer or less, applying a plasma processing device including aRadial Line Slot Antenna (RLSA), and a SiN film, formed in about 2nanometers on this oxide-nitride film by CVD.

When an RLSA-type plasma processing device is applied, a morehigh-quality film with less dangling bond is formed, compared to beingformed by a CVD. Also, because the film forming processing, applying theRLSA plasma processing, is conducted in a relatively low temperature(250°˜450°), the damage of the film surface is decreased compared toother plasma processing. In this way, films formed by applying theRSLA-type plasma processing is high in quality, therefore annealing in ahigh temperature, at about 1000°, is not necessary, and diffusion ofdopant can be prevented. Here, the aforementioned stacking gateinsulator applies the SiN film as the high-permittivity film. Therelative permittivity of the SiN film is about 8, therefore the EOT ofthe SiN film is only about 0.5 (= 4/8) times the effective filmthickness. Due to this, when the SiN film is applied, there is a limitto securing a sufficiently thick physical film thickness, and gaining asufficiently thin EOT by answering to the demand of miniaturization.

By this, when inorganic insulation films with higher relativepermittivity, for example, aluminum oxide (relative permittivity:11),zirconium oxide (24), and hafnium oxide (25) are applied, an EOT about0.17 (= 4/24) times the effective film thickness can be gained.

As aforementioned, by applying an inorganic high-permittivity film, arequested gate insulator having the requested permittivity can begained. However, if an organic high-permittivity film is directly formedonto the silicon oxide film, the silicon oxide film and the organic filmwill cause a reaction. By this, the EOT of the whole stacking gateinsulator will increase.

Generally, the aforementioned inorganic high-permittivity films areformed, for example, by applying an organic metal such as ethoxide metalas the precursor, by CVD. By this, the formed high-permittivity filmincludes a few percent of carbon. When the carbon content is high,reliability declines, such as the occurrence of the leakage currentincreasing.

In this way, hitherto, it was difficult to generate a highly reliablegate insulator having a sufficient physical thickness and a sufficientlythin EOT.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide a forming method andforming system for insulation film, in which a highly reliableinsulation film can be produced.

To achieve the object, the forming method according to a first aspect ofthe present invention comprises;

-   -   a silicon oxide film forming process for forming a silicon oxide        film on the surface region of a silicon substrate;    -   a silicon nitride film forming process for forming a silicon        nitride film on the surface region of the aforementioned silicon        oxide film; and    -   a forming process for forming a permittivity film with a higher        permittivity than the silicon oxide film on the aforementioned        silicon nitride film,    -   wherein:    -   the aforementioned oxide film forming process comprises a        forming method for forming the silicon oxide film on the surface        region of the aforementioned silicon substrate by subjecting the        surface of said silicon substrate to a plasma, generated by        irradiating microwave from a plane antenna having plural slits,        to an oxygen containing gas; and    -   the aforementioned nitride film forming process comprises a        forming method for forming the silicon nitride film on the        surface region of the aforementioned silicon oxide film by        subjecting the surface of the aforementioned silicon oxide film        to a plasma, generated by irradiating microwave from a plane        antenna having plural slits, to a nitride containing gas.

It is preferable that the aforementioned oxide film forming processincludes a process for reforming the oxide film already existing on theaforementioned silicon substrate, by subjecting the surface of theaforementioned silicon substrate to a plasma, generated by irradiatingmicrowave, from a plane antenna having plural slits, to an oxygencontaining gas.

It is preferable that the aforementioned oxide film forming processcomprises a process for exposing the surface of the aforementionedsilicon substrate, and a process for oxidizing the surface region of theaforementioned silicon substrate, by subjecting the exposed surface ofsaid silicon substrate to a plasma, generated by irradiating microwavefrom a plane antenna having plural slits, to an oxygen containing gas.

It is preferable that the aforementioned nitride film forming processcomprises a process for nitriding the surface region of theaforementioned, silicon oxide film, by subjecting the surface of theaforementioned silicon oxide film to a plasma, generated by irradiatingmicrowave from a plane antenna having plural slits, to a nitrogencontaining gas.

The aforementioned permittivity film is comprised of metal as the maincomponent, and may further comprise a permittivity film reformingprocess, for reforming the aforementioned permittivity film bysubjecting the surface of the permittivity film to a plasma, generatedby irradiating microwave from a plane antenna having plural slits, to anoxygen containing gas.

In the aforementioned oxide film forming process, the silicon oxide filmis formed at a thickness of 1 nm˜20 nm, and in the nitride film formingprocess, the nitride film is formed at a thickness of 0.5 nm˜6 nm.

It is preferable that the aforementioned gas comprises argon.

The aforementioned insulation film comprises a gate insulator of aMISFET.

To achieve the aforementioned object, a forming system of an insulationfilm according to the second aspect of the present invention comprises:

an oxide film forming unit for forming a silicon oxide film on thesurface region of a silicon substrate;

a nitride film forming unit for forming a silicon nitride film on thesurface region of the silicon oxide film; and

a permittivity film forming unit for forming a permittivity film of ahigher relative permittivity, than the silicon oxide film, on theaforementioned silicon nitride film;

-   -   wherein:

the oxide film forming unit forms a silicon oxide film on the surfaceregion of the silicon substrate, by exposing the surface of the siliconsubstrate to a plasma, generated by irradiating microwave from a planeantenna having plural slits, to an oxygen containing gas; and

-   -   the nitride film forming unit forms a silicon nitride film on        the surface region of the silicon oxide film, by exposing the        surface of the silicon oxide film to a plasma, generated by        irradiating microwave from a plane antenna having plural slits,        to a nitrogen containing gas.

It is preferable that the oxide film forming unit reforms the oxidefilm, already existing on the silicon substrate, by exposing the surfaceof the silicon substrate to a plasma, generated by irradiating microwavefrom a plane antenna having plural slits, to an oxygen containing gas.

It is preferable that the oxide film forming unit exposes the surface ofthe silicon substrate, and the oxide film forming unit oxides thesurface region of the silicon substrate by exposing the surface of thesilicon substrate to a plasma, generated by irradiating microwave from aplane antenna having plural slits.

It is preferable that the nitride film forming unit nitrides the surfaceregion of the silicon oxide film by exposing the surface of the siliconoxide film to a plasma, generated by irradiating microwave from a planeantenna having plural slits to nitride containing gas.

The permittivity film is comprised of metal as the main component, andmay further comprise a permittivity film reforming unit for reformingthe permittivity film, by exposing the surface of the permittivity filmto a plasma, generated by irradiating microwave from a plane antennahaving plural slits.

The oxide film forming unit forms the silicon oxide film of a thicknessof 1 nm to 20 nm, and the nitride film forming unit forms the nitridefilm of a thickness of 0.5 nm to 6 nm.

It is preferable that the aforementioned gas comprises argon.

The aforementioned insulation film comprises a gate insulator of aMISFET.

BRIEF DESCRIPTION OF DRAWINGS

These objects and other objects and advantages of the present inventionwill become more apparent upon reading of the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a diagram showing the structure of a gate insulator, accordingto the embodiment of the present invention;

FIG. 2 is a diagram showing the structure of a forming system of thegate insulator, according to the embodiment of the present invention;

FIG. 3 is a diagram showing the structure of an etching unit, accordingto the embodiment of the present invention;

FIG. 4 is a diagram showing the structure of an oxidation processingunit, according to the embodiment of the present invention;

FIG. 5 is a top view of a RLSA, according to the embodiment of thepresent invention; and

FIG. 6 is a diagram showing the structure of a CVD unit, according tothe embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The forming method of the insulation film according to the embodiment ofthe present invention will be described referring to the drawings.

The insulation film, formed according to the embodiment of the presentinvention, comprises a gate insulator of a Metal Insulator SemiconductorField Effect Transistor (MISFET) shown in FIG. 1.

As shown in FIG. 1, MISFET 100 comprises, a P-type drain region 102 andsource region 103 in the surface region of an N-type silicon substrate101, a gate insulator 104 formed on the surface region (channel region)of the silicon substrate 101, which is placed between the P-type drainregion 102 and source region 103, and a gate electrode 105 formed on thegate insulator 104. Drain region 102 and source region 103, arerespectively connected to a drain electrode and source electrode,comprising a MISFET 100. Silicon substrate 101, drain region 102 andsource region 103, respectively may be opposite conductivity types.

On the silicon substrate 101, placed between the drain region 102 andsource region 103, the gate electrode 105 is provided via the gateinsulator 104. The gate electrode 105 is comprised of polycrystallinesilicon (p-Si). The gate electrode 105 comprises the MISFET 100, andwhen the gate threshold voltage is applied to the gate electrode 105, achannel (ch) is formed on the surface of the silicon substrate 101 underthe gate insulator 104, and the source and the drain are connected.

The gate insulator 104 is comprised of a silicon oxide film (SiO₂ film)106, a silicon nitride film (SiN film) 107, and a high-permittivity film108.

The silicon oxide film 106 is formed on the surface region (channel ch)of the silicon substrate 101. The silicon oxide film 106 is formed bythe oxidation processing of the surface region of the silicon substrate101, wherein a plasma processing device having a Radial Line SlotAntenna (RLSA) is applied. The silicon oxide film 106 is, for example,formed in a thickness of 0.5 nm to 14 nm.

The silicon nitride film 107 is stacked on the silicon oxide film 106.The silicon nitride film 107 is formed by the nitriding processing ofthe silicon oxide film 106 applying the RLSA type plasma processingdevice. The silicon nitride film 107 is, for example, formed in athickness of 0.5 nm to 6 nm.

The high-permittivity film 108 is placed between the silicon nitridefilm 107 and the gate electrode 105. The high-permittivity film 108 iscomprised of inorganic (metal) materials, such as Al₂O₃, HfSiO₂, Ta₂O₂,ZrSiO₃, HfO₂, and ZrO₂. The high-permittivity film 108 is formed, forexample in a thickness of 1 nm to 20 nm by CVD (Chemical VaporDeposition). Here, the high-permittivity film stands for a film having ahigher dielectric constant than that of the silicon oxide film (about4).

Next, the forming method of the above-mentioned gate insulator 104 willbe described referring to the drawings.

FIG. 2 shows the composition of a forming system 10 of a gate insulatoraccording to the embodiment of the present invention. As shown in FIG.2, the forming system 10 of the gate insulator comprises a cassettestation 11, and a processing station 12.

The cassette station 11 includes a cassette mounting table 13, and afirst conveyance room 14. On the cassette mounting table 13, a cassetteC wherein a predetermined number of wafers can be accommodated, isplaced. While a cassette C, accommodating un-processed wafers, ismounted in the cassette mounting table 13, a cassette C, accommodatingprocessed wafers, is transferred out from the mounting table 13.

A first conveyance system 15, having an arm, is placed in the firstconveyance room 14. The first conveyance system 15 transfers in theaccommodated wafer in a cassette C to the side of the processing station12, while it transfers out the processed wafer from the side of theprocessing station 12, and accommodates it to a cassette C. The interiorof the first conveyance room 14 is kept clean by the down flow of cleanair.

The processing station 12 comprises a second conveyance room 16, a loadlock unit 17 a, and 17 b, an etching unit 18, an oxidation processingunit 19, a nitriding processing nit 20, a CVD unit 21, an annealing unit22, and a spare unit 23.

Each unit is connected to the circumference of the almostoctagonal-shaped second conveyance room 16 through a gate valve 24.Namely, the processing station 12 comprises a clustered-type system. Thesecond conveyance room 16 includes an exhaust system, etc. and candecompress. Each unit 17 through 23, being isolated by the gate valve24, comprises an exhaust system, and an independent atmosphere from thesecond conveyance room 16 may be formed in the interior.

In the center of the second conveyance room, a second conveyance system25 is placed. The second conveyance system 25 comprises an arm, andtransfers the wafer among each unit 17 through 23.

The load lock unit 17 a, and 17 b are connected to the first conveyanceroom 14 in the cassette station 11. The load lock unit 17 a, functionsas a wafer transferring-in port to the processing station 12, and theload lock unit 17 b, functions as a wafer transferring-out port. Thefirst conveyance system 15 transfers the wafer, accommodated in thecassette C of the cassette mounting table 13, into the load lock unit 17a. The first conveyance system 15 also transfers out the processed waferfrom the load lock unit 17 b, and accommodates it in cassette C.

The etching unit 18 eliminates the native oxide film (silicon oxidefilm), which is formed on the surface of the wafer (hereinafter waferW). FIG. 3 is a sectional view showing a structure of the etching unit18.

As shown in FIG. 3, the etching unit 18 comprises a chamber 26, and aplasma forming tube 27.

The chamber 26 is comprised of aluminum, etc. and is formed in an almostcylindrical shape. In the interior of the chamber 26, a mounting table28 for placing wafer W is provided. The mounting table 28 is supported,for example, by a quartz-made prop installed on the base of the chamber26.

Downwards of the chamber 26, heating lamps 30, such as halogen lamps,are placed to heat the mounting table 28 and the interior of the chamber26 to a predetermined temperature. A transmission window 31 made of amaterial such as quartz, is placed between the chamber 26 and theheating lamps 30. On the bottom of the chamber 26, an irradiationopening 32 is formed, and the ends of the transmission window 31 arebonded airtight to the circumference of the irradiation opening 32. Bythis, the heat waves emitted from the heating lamps 30, irradiate theinterior of the chamber 26 (the opposite side of the mounting table 28)going through the transmission window 31 and irradiation opening 32.

In the circumference of the prop 29 at the bottom of the chamber 26, anexhaust opening 33 is provided. The exhaust opening 33 is connected toan exhaust line having a vacuum pump, etc. The interior of the chamber26 is set at a predetermined pressure by the exhaust line.

On the side wall of the chamber 26, a transferring inlet/outlet 34 isprovided at approximately the same height as the mounting table 28. Thetransferring inlet/outlet 34 is connected to the second conveyance room16, through the gate valve 24. When the gate valve 24 is open, thetransferring in/out of the wafer W is carried out, through transferringinlet/outlet 34.

The plasma forming tube 27 is comprised of a material such as quartz,and is structured in a tube-shape. The plasma forming tube 27 isassembled, piercing through the ceiling of chamber 26. On the upper endof the plasma forming tube 27, a gas feed port 35 is provided, and thisgas feed port 35 is connected to a nitrogen gas source 38 and hydrogengas source 39 through mass flow controllers 36 and 37. By this, a mixedgas of nitrogen (N₂) and hydrogen (H₂) is supplied into the plasmaforming tube 27 through the gas feed port 35. Here, the mixed gas is forexample supplied at nitrogen/hydrogen=100 sccm/10 sccm.

On the upper part of the plasma forming tube 27, a plasma forming unit40 is provided. The plasma forming unit 40 comprises a microwavegenerating source 41, a rectangular waveguide tube 42, and anEvenson-type waveguide tube 43.

The microwave generating source 41 generates a microwave having awavelength of, for example, 2.45 GH_(z). The microwave generated fromthe microwave generating source 41 is supplied into the plasma formingtube 27, through rectangular waveguide tube 42 and Evenson-typewaveguide tube 43. The mixed gas of nitrogen and hydrogen, suppliedthrough the gas feed port 35, is supplied into the interior of theplasma forming tube 27, and supplied microwave activates the mixed gas.By this, a down flow of gas plasma is occurred from the upper part tothe lower part of the plasma forming tube 27.

In the lower end of the plasma forming tube 27, an outlet 44 isprovided. A casing material 45 which communicates with the outlet 44 andspreads downwards in an umbrella-shape or cone-shape, is provided in theoutlet 44. By the casing material 45, the gas flowing out of the outlet44 is diffused and provided to the chamber 26.

Directly below the outlet 44, a ring-shaped showerhead 47, comprisingmany gas holes 46, is placed. The showerhead 47 is connected to thenitrogen trifluoride (NF₃) gas source 50 through a communicating tube 48which pierces through the wall of the chamber 26, and a mass flowcontroller 49 equipped with the communicating tube 48.

NF₃ gas is provided from the showerhead 47, and the NF₃ gas is providedduring the down flow of a mixed gas plasma made of hydrogen andnitrogen. Here, NF₃ is for example provided at 30 sccm. In the plasma,hydrogen and nitrogen are in an active state such as a radical, and NF₃molecules are activated by the collision with these radicals andgenerates radicals such as a fluorine radical by dissociation. The gasprovided on the wafer W is in a plasma state, including gas such asnitrogen radical, hydrogen radical, and fluorine radical, etc.

When the plasma, formed in the aforementioned way, contacts the surfaceof the wafer W, a film including Si, N, H, F and O (it has not beenspecifically clarified) is formed on the surface of the wafer W. Thisfilm easily sublimes when the wafer W is heated to a temperature higherthan 100° C., and is eliminated from the surface of the wafer W. In theabove-mentioned way, the native oxide film (SiO₂ film) on the surface ofthe wafer W, is eliminated by the down flow of the plasma.

On the surface of the silicon substrate which the native oxide film(SiO₂ film) is eliminated, many silicon dangling bonds exist, but thesebond with the hydrogen (radical) in the plasma. By this, the surface ofthe substrate is stabilized.

The oxidation processing unit 19 is an RLSA (Radial Line SlotAntenna)-type processing device. The oxidation processing unit 19generates the plasma of the processing gas by using microwave energy,and by this plasma, oxidizes the surface of a silicon substrate 101, andforms a silicon oxide film 106.

The section structure of the oxidation processing unit 19 is shown inFIG. 4. As shown in FIG. 4, the oxidation processing unit 19 comprisesan almost cylindrical chamber 51. The chamber 51 is comprised ofaluminum, etc.

In the center of the chamber 51, a mounting table 52 of thesemiconductor wafer (hereinafter wafer W), which is subjected toprocessing, is placed. In the mounting table 52, a temperature controlunit, which is not shown in the diagrams, is embedded, and by thetemperature control unit, wafer W is heated to a predeterminedtemperature, for example, from room temperature to 600° C.

On the side wall of the chamber 51, a transferring inlet/outlet 53 isprovided at approximately the same height as the top surface of themounting table 52. The transferring inlet/outlet 53 is connected to thesecond conveyance room 16 through gate valve 24. When the gate valve 24is open, the transferring in/out of wafers W is carried out through thetransferring inlet/outlet 53.

One end of an exhaust tube 54 is connected to the bottom of the chamber51, and the other end is connected to an exhaust system 55 such as avacuum pump. The interior of the chamber 51 is set at a predeterminedpressure by the exhaust system 55, etc. for example at a pressure from4.0 Pa to 0.13 kPa (30 mTorr to 1 Torr).

Gas supply tubes 56 are placed in the upper side of the chamber 51. Thegas supply tubes 56 are connected to an Oxygen (O₃) gas source 57, aHydrogen (H₂) gas source 58, and Argon (Ar) gas source 59. The gassupply tubes 56 are placed uniformly, for example in 16 places, alongthe side wall of the chamber 51, in a circle direction. By being placedthis way, the gas provided by the gas supply tubes 56, is providedequally to the upward of the wafer W on the mounting table 52.

An aperture 60 is provided on the upper side of the chamber 51. A window61 is provided in the interior of the aperture 60. The window 61comprises transmission material, for example quartz, and SiO₂ glass,inorganic material such as Si₃N₄, NaCl, KCl, LiF, CaF₂, BaF₂, Al₂O₃,AlN, MgO, and films or sheets of organic material such as polyethylene,polyester, polycarbonate, cellulose acetate, polypropylene,polyvinylchloride, polyvinylidenechloride, polystyrene, polyamide, andpolyimide.

For example, a Radial Line Slot Antenna 62 (hereinafter RLSA) isprovided on top of the window 61. On top of the RLSA 62, a waveguide 64connected to a high-frequency power source unit 63, is provided.Waveguide 64 comprises, a flat circular waveguide tube 65 wherein thebottom end is connected to the RLSA 62, a cylindrical waveguide tube 66wherein one end is connected to the top surface of the circularwaveguide tube 65, a coaxial waveguide converter 67 which is connectedto the top surface of the cylindrical waveguide tube 66, and arectangular waveguide tube 68 wherein one end is connected in a rightangle to the side of the coaxial waveguide converter 67, and the otherend is connected to the high-frequency power source unit 63. RLSA 62 andwaveguide 64 are comprised of copper plates.

In the interior of the cylindrical waveguide tube 66, a coaxial waveguide tube 69 is placed. The coaxial wave guide tube 69 is comprised ofan axis member made of electrically conductive material, and one end ofthe tube is connected to nearly the center of the top surface of theRLSA 62, and the other end thereof is connected coaxially to the topsurface of the cylindrical wave guide tube 66.

FIG. 5 shows a plan view of RLSA 62. As shown in FIG. 5, RLSA 62comprises plural slots 62 a, 62 a, . . . , which are provided on thesame circle, on the surface. Each slot 62 a is an almost rectangleperforated trench, and the adjacent slots 62 a are placed so that theyare at a right angle with each other and form an almost letter of T. Thelength and placement interval of the slot 62 a is determined, accordingto the wavelength of the high-frequency wave generating from thehigh-frequency power source unit 63.

The high-frequency power source unit 63 generates a microwave of forexample 2.45 GHz at a power of for example 500 to 5 kW. The microwavegenerated from the high-frequency power source unit 63, is transferredto the interior of the rectangular waveguide tube 68 at a rectangularmode. Furthermore, the microwave is transformed from the rectangularmode to a circular mode in the coaxial waveguide converter 67, and istransferred to the cylindrical waveguide tube 66 at the circular mode.The microwave is further transferred in a spread state by the circularwaveguide tube 65, and is irradiated from the slot 62 a of the RLSA 62.The irradiated microwave transmits the window 61, and is infused intothe chamber 51.

The interior of the chamber 51 is set at a predetermined vacuumpressure, and mixed gas of Ar, O₂, and H₂ is supplied to the interior ofthe chamber 51, for example at Ar/O₂/H₂=10:1:1, from the gas supply tube56. By the microwave transmitting the window 61, high-frequency waveenergy is conveyed to the mixed gas in the interior of the chamber 51,and high-frequency plasma is generated. At this time, because themicrowave is irradiated from the many slots 62 a of the RLSA 62, ahigh-density plasma is generated. Here, activated species in the plasmaformed by using the RLSA 62, has an electron temperature of about 0.7 to2 eV. In this way, according to the RLSA 62, plasma-activated specieswhich activate relatively placidly is formed.

By an exposure to the generated high-density plasma, an oxidation of thewafer W surface is carried out. Namely, the Ar radical in the generatedplasma, provides energy by acting to the silicon substrate of the waferW surface, and cuts the Si bonding with each other. Furthermore, oxygen(O) radical forms a Si—O bonding with Si. In this way, the surface ofthe silicon substrate is oxidized, and a silicon oxide film of, forexample 1 nm to 20 nm, is formed.

At this time, an H radical which generates from H₂ bonds with the Sidangling bond, and stabilizes the formed silicon oxide film and improvesthe film quality.

The nitriding processing unit 20 is the same RLSA-type plasma processingdevice as the oxidation processing unit 19. The nitriding processingunit 20 forms a silicon nitride film 107 by nitriding a part of thesurface of the silicon oxide film 106, formed in the oxidationprocessing unit 19.

The nitriding processing unit 20 has almost the same structure as theoxidation processing unit 19 shown in FIG. 3. What differs from theoxidation processing unit 19 is that nitrogen (N₂) gas is appliedinstead of oxygen (O₂) gas. In the nitriding processing, a mixed gas ofAr, N₂, and H₂ is applied at the ratio of, for example, Ar/N₂/H₂=10:1:1.

The gas applied instead of oxygen may be any gas including nitrogen suchas NH₃, N₂O, NO, and NO₂.

The silicon oxide film (SiO₂ film) formed on the surface of the wafer Wby the plasma processing of the nitride processing 20, according to theaction of the activated Ar radical, the Si—O bonding is cut.Furthermore, by the nitrogen (N) radical, generated from a gascontaining nitrogen, bonding with this dissociated Si, a Si—N bond isgenerated. In this way, a part of the surface of the silicon oxide filmis nitrided, and a silicon nitride (SiN) film 107 of 0.5 nm to 6 nm isformed.

The CVD unit 21 forms a high-permittivity film 108, here a tantalumoxide (Ta₂O₅) film, on the surface of the wafer W, wherein the nitrideprocessing is carried out, and the SiN film 107 is formed. FIG. 6 showsa plan structure of the CVD unit 21.

As shown in FIG. 6, the CVD unit 21 comprises an almost cylindricalchamber 70. The chamber 70 is for example comprised of aluminum. In thecenter of the interior of the chamber 70, a susceptor 71 for conservingthe wafer W, is provided.

On the upper part of the chamber 70, a showerhead 73 having plural gassupply holes 72, is provided so that it opposes the susceptor 71. Aprocessing gas supply line is connected to the showerhead 73. Aprocessing gas source 74 is connected to the processing gas supply line.

In this example where a Ta₂O₅ film is being formed, the processing gascomprises, for example, organic tantalum gas which is heat-vaporized to100° C. to 200° C., for example, penta-ethoxy-tantalum gas (Ta(OC₂H₅)₅)and nitrogen gas which includes oxiding gas and moisture, and inactivegas as a carrier gas, for example argon gas. These processing gas arebonded just before or in advance, and supplied into the shower head 73,and is supplied to the whole surface of the wafer W through the gassupply holes 72.

In the circumference of the suceptor 71, a baffle plate 76 having pluralbaffle holes 75 is arranged. The gas supplied from the showerhead 73 tothe interior of the chamber 70, flows downward through the baffle hole75. In the bottom part of the chamber 70, plural exhaust ports 77 areprovided. The exhaust ports 77 are connected to the buffer tank 78. Bythe buffer tank 78, the gas supplied to the interior of the chamber 70is once stored, and by this, a uniformity in pressure in the chamber 70can be gained.

Furthermore, the buffer tank 78 is connected to the exhaust line. Theexhaust line connects to a vacuum pump etc., and sets a predeterminedpressure in the interior of the chamber 70, for example at 0.13 kPa (1Torr).

Down below the susceptor 71, a heating room 80, made of quartz etc.,through window 79, is placed. In the heating room 80, plural heatinglamps 81 such as the halogen lamps are provided. By the heating of theheating lamps 81, through window 79, the susceptor 71 (and the interiorof the chamber 70) is set at a predetermined temperature, for example at300° C. to 600° C.

On the side wall of the chamber 70, a transferring inlet/outlet 82 isprovided at approximately the same height as the susceptor 71. Thetransferring inlet/outlet 82 is connected to the second conveyance room16 through the gate valve 24. When the gate valve 24 is open, thetransferring in/out of the wafer W is carried out by the secondconveyance system 25.

In the aforementioned structure of the CVD unit 21, CVD processing iscarried out for example for ten minutes, and for example ahigh-permittivity film (Ta₂O₅ film) 108 of 1 nm to 20 nm is formed onthe SiN film 107 formed by the nitride processing.

The annealing unit 22 has almost the same structure as the oxidationprocessing unit. The annealing (reforming) of the high-permittivity film(metallic insulation film) 108, wherein the film is formed by the CVDunit 21, is carried out in the annealing unit 22. Namely, a precursor(ethoxide metal) originated carbon (C), included in the metallicinsulation film 108, and oxygen plasma reacts, and eliminates as forexample CO and CO₂. By this, a high-quality high-permittivity film 108wherein the carbon content is low, and the gate leakage current etc., isdecreased, can be gained.

Moreover, the processing gas applied in the annealing unit 22, may bedifferent from the gas mixture ratio of the oxidation processing unit19, such as by reducing the oxygen gas ratio.

The spare unit 23 is a multi-purpose unit that is applicable as anotherprocessing unit, for example, as a heating processing unit. To improvethe throughput of the whole forming system 10 of the gate insulator,each above-mentioned unit 17 to 22 may be provided.

Furthermore, the number of spare units 23 is not limited to one, andplural units may be provided.

The forming method of a gate insulator 104 applying the above-mentionedstructure of the forming system 10 of the gate insulator 104 will bedescribed below, referring to FIG. 2.

First, wafers W each having a formed drain region 102 and a sourceregion 103, are prepared. These wafers W, are accommodated into thecassette C in predetermined numbers, for example every 25, and mountedon the cassette mounting table 13 of the cassette station 11.

The first conveyance system 15 takes out the wafer W from the interiorof the cassette C, and mounts it inside the load lock unit 17 a. Then,the load lock unit 17 a is closed, and almost the same pressure is setas the second conveyance room 16. After that, the gate valve 24 isopened, and the second conveyance system 25 takes out the wafer W fromthe load lock unit 17 a.

The second conveyance unit 25 transfers in the wafer W to the etchingunit 18, and mounts it on the mounting table 28. Then, the gate valve 24is closed, and the interior of the etching unit 18 is set at apredetermined pressure.

In the etching unit 18, etching, using the downflow of the plasma gascomprised of N₂, H₂, and NF₃, is carried out. By this, the native oxidefilm (SiO₂ film), formed on the surface of the wafer W, is eliminated.Also, at the same time, on the dangling bond of the silicon (Si) of thesurface of the wafer W, hydrogen (H) is bonded, and a stable film isformed.

After the etching processing, the interior of the etching unit 18 is setat a pressure almost the same as the conveyance room 16. Subsequently,the gate valve 24 is opened, and the wafer W is transferred out of theetching unit 18 by the second conveyance system 25.

The wafer W is subsequently sent to the oxidation processing unit 19.The second conveyance system 25 is mounted on the mounting table 52 inthe interior of the oxidation processing unit 19. Then, the gate valve24 is closed, and a predetermined pressure in the interior of theoxidation processing unit 19 is set.

The oxidation processing of a surface of a silicon substrate 101, iscarried out by the RLSA-type plasma processing device in the oxideprocessing unit 19. By this, a silicon oxide of for example 1 nm to 20nm is formed on the surface of the silicon substrate 101.

After the oxidation processing, the interior of the oxide processingunit 19 is set at almost the same pressure as the second conveyance room16. Next, the second conveyance room 25 transfers in the wafer W to theinterior of the etching unit. Then, the gate valve 24 is opened, and thewafer W is transferred out of the oxidation processing unit 19 by thesecond conveyance system 25. After the wafer W is transferred in, thegate valve 24 is closed, and the interior of the nitriding processingunit 20 is set at a predetermined pressure.

The nitriding processing of the surface of the silicon substrate 101 iscarried out by the RLSA plasma processing device, in the nitridingprocessing unit 20. By this, the surface of the silicon oxide film isnitrided. By this, a part of the silicon oxide film, a silicon nitridefilm 107 of for example 0.5 nm to 6 nm is formed.

After the nitriding processing, the interior of the nitriding processingunit 20 is set at almost the same pressure as the second conveyance room25. Then, the gate valve 24 is opened, and the wafer W is transferredout of the nitriding processing unit 20 by the second conveyance system25. Next, the second conveyance system 25 transfers in the wafer W intothe interior of the CVD unit 21. After the transferring in of the waferW, the gate valve 24 is closed, and the interior of the CVD unit 21 isset at a predetermined pressure.

A high-permittivity film 108, for example a tantalum oxide film isformed on the silicon nitride film 107 by the CVD method in the CVD unit21. The high-permittivity film 108 is formed at a thickness of forexample 1 nm to 20 nm.

After the CVD processing, the interior of the CVD unit 21 is set at apredetermined pressure almost the same as the second conveyance room 16.Then, the gate valve 24 is opened, and wafer W is transferred out of theCVD unit 21 by the second conveyance system 25. Next, the secondconveyance system 25 transfers in the wafer W into the interior of theannealing unit 22. After the transferring in of the wafer W, the gatevalve 24 is closed, and the interior of the annealing unit 22 is set ata predetermined pressure.

Annealing processing applying the RLSA-type plasma processing device isperformed to the wafer W, in the annealing unit 22. Namely, low-energyoxygen gas plasma is exposed to a high-permittivity film 108, and thecarbon (C) in the film is eliminated.

After the annealing processing, the interior of the annealing unit 22 isset at about the same pressure as the second conveyance room 16. Then,the gate valve 24 is opened, and the wafer W is transferred out of theannealing unit 22 by the second conveyance system 25. Then, the secondconveyance system 25 transfers in the wafer W into the load lock unit 17b. After the wafer W is transferred in, the gate valve 24 is closed, andthe interior of the load lock unit 17 b is set at almost the samepressure as the first reaction room.

Then, the first conveyance system 15 transfers out the wafer W from theload lock unit 17 b, and accommodates them in the cassette C on thecassette mounting table 13. The forming process of a gate insulationfilm 104 comprising a silicon oxide 106, a silicon nitride film 107, anda high-permittivity film 108 is completed in the above-mentionedprocess.

The present invention is not limited to the aforementioned embodiments,and various modifications and applications are possible. Themodifications which may be applied in the aforementioned embodiment ofthe present invention will be described below.

The structure of the etching unit 18 in the aforementioned embodiment,is only one example, and the structure may be of any kind as long as thestructure can effectively eliminate the native oxide (SiO₂) formed onthe surface of the wafer W. The structure of the CVD unit 21 is alsoonly one example, and the structure may be of any kind as long as it ispossible to form a tantalum oxide film on the SiN film. Furthermore, astructure fit for forming a high-permittivity film, besides the tantalumoxide, is possible.

In the aforementioned embodiment, an etching unit 18 is provided, andthe native oxide film on the surface of the wafer W, is eliminated.However, instead of providing an etching unit 18, a structure whichdirectly reforms a low quality silicon oxide film (native oxide film) toa high quality silicon oxide film 106, by the oxidation processing unit,is possible.

In the aforementioned embodiment, the oxide film forming processing,nitride film forming processing, and the annealing processing is carriedout respectively in the oxidation processing unit 19, nitridingprocessing unit 20, and annealing unit 22. However, it may be carriedout in the same unit, by for example integrating the gas supply units.Of course it is preferable that the processing is conducted in differentunits, from the viewpoint of throughput and safety.

In the aforementioned embodiment, the RLSA 62 and the waveguide 64,applied in the oxidation processing unit 19, nitriding processing unit20, and annealing unit 22, is comprised of copper plate. Here, tocontrol the conveyance loss of the microwave, the materials thatcomprise the RLSA 62 and the waveguide 64, may be high-permittivity Al,Cu, Ag/Cu coated stainless steel.

Also, the direction of the feed port to the circular waveguide 64, maybe a direction wherein the microwave is supplied parallel to an H-planesuch as an H-plane T-branch or in a direction parallel to a tangent, ora direction wherein the microwave is supplied vertically to an H-plane,such as an E-plane T-branch, as long as the microwave is effectivelysupplied into the microwave conveyance space, in the interior of thecircular waveguide 64. Furthermore, ½ or ¼ of the wavelength in thetube, is the suitable slot interval of the wave direction of themicrowave.

Furthermore, using a microwave of wavelength 2.45 GHz, a high-densityplasma is generated. However, it is not limited to this, and themicrowave frequency can be chosen accordingly, from the range of 0.8 GHzto 20 GHz.

The gas applied to oxidation and nitriding etc., is not limited to theaforementioned gas. For example instead of Ar, other noble gas such asXe, Ne, Kr, and Hr may be applied. However, to control the damage to thefilm surface, and to effectively cut the bonding of the SiO₂, it ispreferable to apply Ar.

When nitriding, nitrogen-containing gas such as NH₃, N₂O, NO, NO₂, maybe applied besides N₂.

Moreover, the aforementioned mixed gas ratio of the mixed gas, is notlimited to the aforementioned ratio (Ar/N₂/(O₂)/H₂/=1:0:1:1), and forexample, the abundance ratio of N₂ (O₂), H₂, may be changed respectivelyin a range from 0.05 to 5. Furthermore, reaction conditions concerningthe wafer temperature, and reaction pressure etc., is not limited to theabove-mentioned examples, and may be of any kind as long as ahigh-quality SiN film is formable.

In the aforementioned embodiment, the annealing unit 22 eliminates thecarbon in the high-permittivity film using the RLSA-type plasmaprocessing device, but a structure omitting the annealing unit 22 ispossible. Of course, it is needless to say that a structure comprisingan annealing unit 22 forms a more high-quality film.

In the aforementioned embodiment, the film in the bottom layer of thestacking gate insulator 104 is a silicon oxide film 106, but it may be afilm containing silicon such as a silicon nitride film or a siliconoxide-nitride film. In this case, the kind of gas used in the oxidationprocessing unit 19 is changed. For example, if a silicon nitride (SiN)film is going to be formed, nitrogen gas is used instead of oxygen gas,and if a silicon oxide-nitride (SiON) film is going to be formed, it maybe a structure further adding nitrogen gas.

INDUSTRIAL APPLICABILITY

In the aforementioned embodiment, an inorganic (metal) series as ahigh-permittivity film 108 was applied. However, other films comprisedof SiC, SiN, etc., formed by CVD etc., may be used. In this case, theSiN film formed by the RLSA plasma functions as a film that prevents thepenetration of impurities from the gate electrode (polycrystallinesilicon) to the silicon substrate.

In the aforementioned mode, the gate electrode 105 of the MISFET 100, iscomprised of polycrystalline silicon. However, it is not limited tothis, and may be comprised of silicon-germanium.

In the aforementioned embodiment, the gate insulator 104 of the MISFET100 is formed. However, it is not limited to this, and it is possible toapply the forming of the gate insulator in the present invention, toother devices such as a flash memory.

As described above, according to the present invention, a forming methodand a forming system of a highly reliable gate insulator will beprovided.

Various embodiments and changes may be made thereunto without departingfrom the broad spirit and scope of the invention. The above-describedembodiment is intended to illustrate the present invention, not to limitthe scope of the present invention. The scope of the present inventionis shown by the attached claims rather than the embodiment. Variousmodifications made within the meaning of an equivalent of the claims ofthe invention and within the claims are to be regarded to be in thescope of the present invention.

This application is based on Japanese Patent Application No. 2001-260179filed on Aug. 29, 2001 and including specification, claims, drawings andsummary. The disclosure of the above Japanese Patent Application isincorporated herein by reference in its entirety.

1. An insulation film forming system comprising: an oxide film formingunit for forming a silicon oxide film on a surface region of a siliconsubstrate; a nitride film forming unit for forming a silicon nitridefilm on a surface region of said silicon oxide film; and a permittivityfilm forming unit for forming a permittivity film of a higherpermittivity, than the silicon oxide film, on said silicon nitride film;wherein: said oxide film forming unit forms the silicon oxide film onthe surface region of said silicon substrate, by exposing the surface ofsaid silicon substrate to a plasma, generated by irradiating microwavefrom a plane antenna (62) having plural slits, to an oxygen containinggas; and said nitride film forming unit forms the silicon nitride filmon the surface region of said silicon oxide film, by exposing thesurface of said silicon oxide film to a plasma, generated by irradiatingmicrowave from a plane antenna of said silicon nitride film forming unithaving plural slits, to a nitrogen containing gas.
 2. The insulationfilm forming system according to claim 1, wherein said oxide filmforming unit reforms a low quality silicon oxide film already existingon said silicon substrate by exposing the surface of said low qualitysilicon oxide film to a plasma, generated by irradiating microwave froma plane antenna having plural slits, to the oxygen containing gas,instead of forming the silicon oxide film on the surface of said siliconsubstrate.
 3. The insulation film forming system according to claim 1,wherein said oxide film forming unit exposes the surface of said siliconsubstrate, and oxidizes the surface region of said silicon substrate byexposing the surface of said silicon substrate to the plasma, generatedby irradiating microwave from said plane antenna having plural slits, tothe oxygen containing gas.
 4. The insulation film forming systemaccording to claim 1, wherein said nitride film forming unit nitridesthe surface region of said silicon oxide film by exposing the surface ofsaid silicon oxide film to the plasma, generated by irradiatingmicrowave from said plane antenna of said nitride film forming unithaving plural slits, to the nitrogen containing gas.
 5. The insulationfilm forming system according to claim 1, wherein said permittivity filmis comprised mainly of metal, and further comprises a permittivity filmreforming unit for reforming said permittivity film, by exposing thesurface of said permittivity film to a plasma, generated by irradiatingmicrowave from a plane antenna having plural slits to an oxygencontaining gas.
 6. The insulation film forming system according to claim5, wherein said permittivity film reforming unit eliminates carbon insaid permittivity film by the plasma of said oxygen containing gas. 7.The insulation film forming system according to claim 1, wherein saidoxide film forming unit forms said silicon oxide film of a thicknessfrom 1 nm to 20 nm, and said nitride film forming unit forms saidnitride film of a thickness from 0.5 nm to 6 nm.
 8. The insulation filmforming system according to claim 1, wherein said oxygen containing gasor said nitrogen containing gas comprises argon.
 9. The insulation filmforming system according to claim 1, wherein said insulation filmcomprises a gate insulator film of a MISFET.
 10. An insulation filmforming system, comprising: a cassette for accommodating a substrate; afirst conveyance room which transfers said substrate to or from saidcassette; a processing unit which processes said substrate; a secondconveyance room which transfers said substrate to or from saidprocessing unit; and a load lock which transfers said substrate betweensaid first conveyance room and said second conveyance room, wherein saidprocessing unit comprises: an oxide film forming unit which forms anoxide film on a surface of said substrate by exposing the surface ofsaid substrate to a plasma, generated by irradiating high-frequencyenergy to an oxygen containing gas via an antenna; and a nitride filmforming unit which forms a nitride film on a surface of said oxide filmby exposing the surface of said oxide film to a plasma, generated byirradiating high-frequency energy to a nitrogen containing gas via anantenna.
 11. The insulation film forming system according to claim 10,wherein said antennas of said oxide film forming unit and said nitridefilm forming unit are plane antennas having plural slits.
 12. Theinsulation film forming system according to claim 10, comprising a CVDunit which forms a permittivity film having a high permittivity on saidnitride film.
 13. The insulation film forming system according to claim10, further comprising a unit which eliminates a natural oxide filmexisting on said substrate.
 14. The insulation film forming systemaccording to claim 13, wherein said unit which eliminates a naturaloxide film comprises: a chamber which transfers said substrate out; aplasma forming tube which has a first gas inlet for introducing a firstgas, activates said gas, and supplies said gas into said chamber; and asecond gas inlet which is disposed under said plasma forming tube, forintroducing a second gas into said chamber.
 15. The insulation filmforming system according to claim 14, wherein said first gas comprises anitrogen gas and an oxygen gas, and said second gas comprises an NF₃gas.
 16. The insulation film forming system according to claim 14,wherein said unit comprises a heating unit.
 17. The insulation filmforming system according to claim 10, comprising an annealing unit whichanneals said substrate on which said nitride film has been formed. 18.The insulation film forming system according to claim 10, furthercomprising a high-frequency power source which supplies microwave tosaid antenna of said oxide film forming unit or said nitride filmforming unit.
 19. An insulation film forming system, comprising: acassette for accommodating a substrate; a processing unit whichprocesses said substrate; a first conveyance room to which a load lockis connected; a second conveyance room which is connected to saidprocessing unit; a first conveyance mechanism arranged in said firstconveyance room, which transfers said substrate from said cassette tosaid load lock or from said load lock to said cassette; and a secondconveyance mechanism arranged in said second conveyance room, whichtransfers said substrate from said load lock to said processing unit orfrom said processing unit to said load lock, and transfers saidsubstrate between each said processing unit, wherein said processingunit comprises: an oxide film forming unit which forms an oxide film ona surface of said substrate by exposing the surface of said substrate toa plasma, generated by irradiating high-frequency energy to an oxygencontaining gas via an antenna; and a nitride film forming unit whichforms a nitride film on a surface of said oxide film by exposing thesurface of said oxide film to a plasma, generated by irradiatinghigh-frequency energy to a nitrogen containing gas via an antenna. 20.The insulation film forming system according to claim 19, wherein saidantennas of said oxide film forming unit and said nitride film formingunit are plane antennas having plural slits.
 21. The insulation filmforming system according to claim 19, comprising a CVD unit which formsa permittivity film having a high permittivity on said nitride film. 22.The insulation film forming system according to claim 19, furthercomprising a unit which eliminates a natural oxide film existing on saidsubstrate.
 23. The insulation film forming system according to claim 19,comprising an annealing unit which anneals said substrate on which saidnitride film has been formed.
 24. An insulation film forming systemcomprising: an oxide film forming unit for forming an oxide film on asurface region of a substrate; a nitride film forming unit for nitridinga part of the surface region of said oxide film, thereby forming anitride film on a surface region of said oxide film; and a permittivityfilm forming unit for forming a permittivity film of a higherpermittivity, than the oxide film, on said nitride film; wherein: saidoxide film forming unit forms said oxide film on the surface region ofsaid substrate, by exposing the surface of said substrate to a plasma,generated by irradiating microwave from a plane antenna having pluralslits, to an oxygen containing gas; and said nitride film forming unitnitrides a part of the surface region of said oxide film, therebyforming said nitride film on the surface region of said oxide film, byexposing the surface of said oxide film to a plasma, generated byirradiating microwave from a plane antenna of said nitride film formingunit having plural slits, to a nitrogen containing gas.
 25. Theinsulation film forming system according to claim 24, wherein saidforming of an oxide film and said forming of a nitride film are carriedout in a same unit.
 26. The insulation film forming system according toclaim 25, comprising an annealing unit which anneals said substrate.